The present invention relates in general to a thermal management device for use with a battery. In particular the present invention relates to a cooling and heating device to effectively cool the battery during rapid charging as well as heat the battery during colder periods.
There have been numerous attempts and initiatives established for next generation land based vehicles. Some programs have set goals for vehicle mileage of 80 miles/gal and greatly reduced vehicle emissions based on today""s standards. Federal and local governments have placed limits on emissions as well as standards for fuel consumption. Even with recovery of regenerative braking energy, a hybrid electric/internal combustion vehicle will be pressed to meet these goals.
Hybrid, all-Electric and internal combustion types of vehicles need a means to store energy on board. For the present, the means of choice are lead-acid batteries, with the hybrid electric vehicle having auxiliary power supplied by a small internal combustion engine. The technology of leadacid batteries is well known in the art and is therefore the battery of choice based upon economics, availability and reliability.
One of the main drawbacks to lead-acid batteries is internal heat buildup as a natural consequence of the discharge process as well as 12R losses during discharge and high rates of charging. This limits the recharging rate of the battery for an electric vehicle, which has a limited range of about 80 miles. To become practical, a quick turnaround on recharge is needed. One of the factors preventing this advancement is heat build-up during quick recharge.
In a hybrid electric vehicle application the auxiliary power unit provides a continuous charge to the battery energy storage system. As such, heat generation in the lead-acid battery is a constant problem that must be addressed to reduce thermal damage to the batteries.
There are many U.S. patents that disclose various attempts aimed at cooling the battery during charging. Pat. No. 4,007,315 discloses liquid coolant tubes disposed in the electrolyte above the plates of the battery attempting to remove the heat generated in the battery. U.S. Pat. No. 5,569,552 discloses a double-walled battery in which to circulate liquid in an attempt to cool the battery. U.S. Pat. Nos. 5,623,195 and 5,121,047 disclose charging schemes, which attempt to limit or reduce the effect of the thermal build-up in the cells during charging. Although these charging schemes are effective in lowering the thermal build-up in batteries during a charge, they disadvantageously prolong the charging cycle.
None of the aforementioned prior art designs are aimed at the heart of the cell of a battery where the thermal energy is produced. What is needed is a thermal management device in batteries that will better manage the heat build-up in the hybrid electric vehicle as well as allowing for a much quicker charge in the all-electric vehicle, reducing the heating problem significantly in the battery energy storage units of these vehicles. It has been estimated that raising the average battery operating temperature by 10xc2x0 C. shortens the lifetime of the battery by half. Therefore, it is of paramount importance that the temperature of the battery, and hence the amount of thermal energy that is produced in the battery, be managed accordingly.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the quick charge battery with thermal management of the present invention.
The operation of the cooling system in one embodiment of the present invention utilizes thermoelectric cooling within the interior of the battery, as well as the exterior surfaces of the battery. The heat generated in the battery due to charging operations can be removed without creating problems in the operation thereof, while increasing the useful lifetime of the battery. In addition, with the thermoelectric cooler (also known as a thermoelectric generator) disposed within the battery it is possible to reverse current flow through the thermoelectric generator, thereby heating the battery under certain circumstances. The invention is therefore applicable to batteries of any type and in any usage where temperature control of the battery interior and/or exterior is desired. Microcoolers can be used in place of thermoelectric coolers or in addition to thermoelectric coolers.
Heat pipes may be used in place of thermoelectric cooling or in addition to thermoelectric cooling. The heat pipe comprises a flat plate heat pipe or thin flat plate heat pipe where electrolyte flows through the heat plate is not desired. In situations where electrolyte movement is desired, the heat pipe comprises an array or grid of smaller heat pipes or a heat pipe having a loop or other open shape.
A heat pipe may be sandwiched in thermal contact with a standard thermoelectric generator to form a cooling module. Preferably, the heat pipe is sandwiched between a pair of standard thermoelectric generators to form a cooling module. A heat pipe may be sandwiched in thermal contact with a microcooler to form an ultrathin cooling module. Preferably, the heat pipe is sandwiched between a pair of microcoolers to form an ultrathin cooling module.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.